Method for manufacturing deposition mask, method for manufacturing display device and deposition mask

ABSTRACT

A method includes: sandwiching a plastic layer between a glass substrate and a metal plate made of an iron-nickel alloy and joining the metal plate to the glass substrate with the plastic layer in between; forming a mask portion including a plurality of mask holes from the metal plate; joining a surface of the mask portion that is opposite to a surface of the mask portion that is in contact with the plastic layer to a mask frame, which has a higher rigidity than the mask portion and is in a shape of a frame surrounding the mask holes of the mask portion; and peeling off the plastic layer and the glass substrate from the mask portion.

BACKGROUND

The present disclosure relates to a method for manufacturing a vapordeposition mask, a method for manufacturing a display device, and avapor deposition mask.

A vapor deposition mask has a contact surface and a non-contact surface.The contact surface is brought into contact with the vapor depositiontarget, such as a substrate, and the non-contact surface is opposite tothe contact surface. The vapor deposition mask has a plurality of maskholes. Each mask hole extends through the vapor deposition mask from thenon-contact surface to the contact surface and includes a non-contactopening, which is in the non-contact surface and through which the vapordeposition material enters, and a contact opening, which is in thecontact surface and faces the vapor deposition target. The vapordeposition material enters through the non-contact opening and proceedsthrough the contact opening so as to be deposited on the vapordeposition target. This forms a pattern corresponding to the positionand shape of the contact opening on the vapor deposition target (seeJapanese Laid-Open Patent Publication No. 2017-145491, for example).

To improve the accuracy of the position and other features of patterns,techniques have been used to manufacture vapor deposition masks in whicheach mask hole has a passage area that decreases monotonically from thenon-contact opening to the contact opening. Further, in recent years,there has been a need for a shorter distance between the non-contactopening and the contact opening, that is, a thinner vapor depositionmask, to improve the uniformity of the film thickness of the pattern.

However, a thinner vapor deposition mask typically fails to havesufficient mechanical durability, considerably increasing the difficultyof handling the vapor deposition mask. Accordingly, there is a strongneed for a technique that achieves both the improvement in the accuracyof features of patterns and the improvement in the handleability ofvapor deposition masks.

SUMMARY

It is an objective of the present disclosure to provide a method formanufacturing a vapor deposition mask, a method for manufacturing adisplay device, and a vapor deposition mask that achieve both theimprovement in the accuracy of the structure of patterns formed by vapordeposition and the improvement in the handleability of the vapordeposition mask.

To achieve the foregoing objective, a method for manufacturing a vapordeposition mask including a mask portion that is formed from a metalplate made of an iron-nickel alloy and has a plurality of mask holes isprovided. The method includes: sandwiching a plastic layer between aglass substrate and a metal plate made of an iron-nickel alloy andjoining the metal plate to the glass substrate with the plastic layer inbetween; forming a mask portion including a plurality of mask holes fromthe metal plate; joining a surface of the mask portion that is oppositeto a surface of the mask portion that is in contact with the plasticlayer to a mask frame, which has a higher rigidity than the mask portionand is in a shape of a frame surrounding the mask holes of the maskportion; and peeling off the plastic layer and the glass substrate fromthe mask portion.

With this configuration, the plastic layer and the glass substratesupport the mask portion having a plurality of through-holes in theprocess of manufacturing the vapor deposition mask. In addition, themask frame supports the mask portion in the vapor deposition mask. Thisallows the mask portion to be thinner than that in a configuration inwhich the vapor deposition mask consists only of the mask portion.Consequently, the shortened distance from one opening to the other ofeach through-hole improves the accuracy of the structure of the pattern,while the rigidity of the mask frame improves the handleability of thevapor deposition mask.

In the above-described method for manufacturing a vapor deposition mask,peeling off the plastic layer and the glass substrate may include:peeling off the glass substrate from the plastic layer by irradiating aninterface between the plastic layer and the glass substrate with a laserbeam having a wavelength that passes through the glass substrate and isabsorbed by the plastic layer; and peeling off the plastic layer fromthe mask portion by dissolving the plastic layer using a chemicalsolution after peeling off the glass substrate from the plastic layer.

This configuration peels off the glass substrate from the plastic layerby irradiation with the laser beam and also peels off the plastic layerfrom the mask portion by dissolving the plastic layer using a chemicalsolution. This reduces the external force acting on the mask portion, ascompared to a configuration that applies an external force to thelaminate of the glass substrate, the plastic layer, and the mask portionto cause interface failure to peel off the glass substrate and theplastic layer from the mask portion. As a result, the peeling of theplastic layer and the glass substrate is less likely to deform the maskportion, and ultimately less likely to deform the through-holes in themask portion.

In the above-described method for manufacturing a vapor deposition mask,at the wavelength of the laser beam, the glass substrate may have ahigher transmittance than the plastic layer.

This configuration increases the efficiency in heating the section ofthe plastic layer that forms the interface between the glass substrateand the plastic layer, as compared to a configuration in which theplastic layer has a higher transmittance than the glass substrate.

In the above-described method for manufacturing a vapor deposition mask,the wavelength of the laser beam may be between 308 nm and 355 nminclusive. Also, the transmittance of the glass substrate at thewavelength may be greater than or equal to 54%, and the transmittance ofthe plastic layer at the wavelength may be less than or equal to 1%.

In this configuration, the glass substrate allows more than half thelight quantity of laser beam applied to the glass substrate to passthrough, and the plastic layer absorbs most of the laser beam that haspassed through the glass substrate. This further increases theefficiency in heating the section of the plastic layer forming theinterface between the glass substrate and the plastic layer.

In the above-described method for manufacturing a vapor deposition mask,the mask frame may be made of an iron-nickel alloy, and a ratio of athickness of the mask frame to a thickness of the mask portion may begreater than or equal to 2.

In this configuration, both of the mask portion and the mask frame aremade of an iron-nickel alloy, and the mask frame is at least twice asthick as the mask portion. This enhances the mechanical strength of thevapor deposition mask. Further, when vapor deposition is performed usingthe vapor deposition mask, the mask portion is unlikely to warp, whichwould be otherwise caused by a difference in thermal expansioncoefficient between the mask frame and the mask portion. This avoidsreduction in the accuracy of the shape of pattern formed using the vapordeposition mask.

In the above-described method for manufacturing a vapor deposition mask,the thickness of the mask frame may be between 50 μm and 200 μminclusive, and the thickness of the mask portion may be between 3 μm and5 μm inclusive. Also, forming the mask portion may include forming themask holes such that 700 or more and 1000 or less mask holes arearranged per inch in a direction along a surface of the mask portion.

In this configuration, even when the thickness of the mask portion isextremely thin, the mask frame that is at least ten times thicker thanthe mask portion avoids reduction in the overall mechanical strength ofthe vapor deposition mask.

In the above-described method for manufacturing a vapor deposition mask,joining the metal plate to the glass substrate with the plastic layer inbetween may include joining the metal plate having a thickness ofgreater than or equal to 10 μm to the glass substrate with the plasticlayer in between. The method may further include etching the metal platebefore the mask portion is formed from the metal plate to reduce athickness of the metal plate to half or less of a thickness of the metalplate before etching.

In this configuration, the metal plate has a higher rigidity than themask portion of the vapor deposition mask. This facilitates the joiningof the metal plate to the glass substrate as compared to a configurationin which the metal plate that is joined to the glass substrate has thesame thickness as the mask portion.

In the above-described method for manufacturing a vapor deposition mask,the plastic layer may be made of polyimide.

In this configuration, the metal plate, the plastic layer, and the glasssubstrate have similar thermal expansion coefficients. Consequently, inthe process of manufacturing the vapor deposition mask, heating thelaminate of the metal plate, the plastic layer, and the glass substrateis unlikely to warp the laminate, which would be otherwise caused by adifference in thermal expansion coefficient between the layers of thelaminate.

In the above-described method for manufacturing a vapor deposition mask,the metal plate may include a first surface and a second surface. Themethod may further include etching the metal plate from the firstsurface before joining the metal plate to the glass substrate. Also,joining the metal plate to the glass substrate may include joining asurface obtained after the first surface is etched to the glasssubstrate with the plastic layer in between. The method may furtherinclude etching the metal plate from the second surface after the metalplate is joined to the glass substrate.

In this configuration, etching both the first and second surfaces of themetal plate reduces the thickness of the metal plate and also reducesthe residual stress of the metal plate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing the structure of a mask device accordingto one embodiment.

FIG. 2 is a cross-sectional view partially showing the structure of amask portion.

FIG. 3 is a cross-sectional view partially showing the joining structurebetween an edge of a mask portion and a mask frame.

FIGS. 4A and 4B are a plan view and a cross-sectional view of thestructure of a vapor deposition mask, showing the relationship betweenthe number of mask holes in the vapor deposition mask and the number ofmask holes in each mask portion.

FIGS. 5A to 5F are process diagrams for illustrating a method formanufacturing a vapor deposition mask according to one embodiment, eachshowing one step in the process.

FIGS. 6A to 6C are process diagrams for illustrating a method formanufacturing a vapor deposition mask according to one embodiment, eachshowing one step in the process.

FIG. 7 is a graph showing the relationship between the wavelength of alaser beam and the amount of displacement in test examples.

FIG. 8 is a graph showing the relationship between the wavelength oflight and the transmittance of each glass substrate in test examples.

FIG. 9 is a graph showing the relationship between the wavelength oflight and the transmittance of each plastic layer in test examples.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Referring to FIGS. 1 to 9, embodiments of a method for manufacturing avapor deposition mask, a method for manufacturing a display device, anda vapor deposition mask are now described. In the followingdescriptions, the structure of a mask device, the joining structure ofthe mask portions of the mask device, the number of the mask portions, amethod for manufacturing a vapor deposition mask, and test examples areexplained in this order.

[Structure of Mask Device]

Referring to FIGS. 1 and 2, the structure of a mask device is nowdescribed.

As shown in FIG. 1, a mask device 10 includes a main frame 20 and aplurality of vapor deposition masks 30. The main frame 20 has arectangular frame shape for supporting the vapor deposition masks 30.The main frame 20 is attached to a vapor deposition apparatus forperforming vapor deposition. The main frame 20 has main frame holes 21,which are equal in number to the vapor deposition masks 30. Each mainframe hole 21 extends through the main frame 20 in substantially theentire area where a vapor deposition mask 30 is placed.

Each vapor deposition mask 30 includes a mask frame 31 and mask portions32. Each mask frame 31 has the shape of a planar strip and supports themask portions 32. The mask frame 31 is attached to the main frame 20.The mask frame 31 has mask frame holes 33, which are equal in number tothe mask portions 32. Each mask frame hole 33 extends through the maskframe 31 in substantially the entire area where a mask portion 32 isplaced. The mask frame 31 has a higher rigidity than the mask portions32 and has a frame shape surrounding the mask frame holes 33. The maskframe 31 has inner edge sections defining the mask frame holes 33. Themask portions 32 are fixed to the inner edge sections by welding oradhesion.

As shown in FIG. 2, each mask portion 32 consists of a mask sheet 32S.The mask sheet 32S may be a single metal sheet or a multilayer metalsheet.

The metal sheet forming the mask sheet 32S is made of an iron-nickelalloy. The material of the metal sheet may be an iron-nickel alloycontaining at least 30 mass % of nickel. Among iron-nickel alloys,Invar, which is an alloy mainly composed of an alloy containing 36 mass% of nickel and 64 mass % of iron, is preferably used for the metalsheet. When the principal component of the metal sheet is the alloy of36 mass % of nickel and 64 mass % of iron, the remainder of the metalsheet may contain additives such as chromium, manganese, carbon, andcobalt.

When the mask sheet 32S is an Invar sheet, the mask sheet 32S has athermal expansion coefficient of about 1.2×10⁻⁶/° C., for example. Themask sheet 32S having such a thermal expansion coefficient allows thedegree of thermal expansion of the mask portion 32 to match that of theglass substrate. Thus, a glass substrate may be suitably used as thetarget of vapor deposition performed using the mask device 10.

The mask sheet 32S includes a mask front surface 32F and a mask backsurface 32R, which is opposite to the mask front surface 32F. The maskfront surface 32F faces the vapor deposition source in a vapordeposition apparatus. The mask back surface 32R is in contact with thevapor deposition target, such as a glass substrate, in the vapordeposition apparatus. The mask back surface 32R is an example of acontact surface, and the mask front surface 32F is an example of anon-contact surface.

The mask sheet 32S may have a thickness of between 1 μm and 15 μminclusive. In particular, when the thickness of the mask sheet 32S isless than or equal to 5 μm, mask holes 32H, which are an example ofthrough-holes formed in the mask sheet 32S, can have a depth of lessthan or equal to 5 μm. Such a thin mask sheet 32S reduces the area inthe vapor deposition target that is hidden by the vapor deposition mask30 as viewed from the vapor deposition particles traveling toward themask sheet 32S, in other words, reduces the shadow effect.

The mask sheet 32S having a thickness of between 3 μm and 5 μm inclusivecan have mask holes 32H that are spaced apart from one another in a planview of the mask front surface 32F and usable to manufacture ahigh-resolution display device having a resolution of between 700 ppiand 1000 ppi inclusive. The mask sheet 32S having a thickness of between10 μm and 15 μm inclusive can have mask holes 32H that are spaced apartfrom one another in a plan view of the mask front surface 32F and usableto manufacture a low-resolution display device having a resolution ofbetween 300 ppi and 400 ppi inclusive.

Each mask portion 32 has a plurality of mask holes 32H extending throughthe mask sheet 32S. The hole side surface defining each mask hole 32H issemicircular and curved outward of the mask hole 32H as viewed in across-section along the thickness direction of the mask sheet 32S.

The mask front surface 32F includes front surface openings H1, which areopenings of the mask holes 32H. The mask back surface 32R includes backsurface openings H2, which are openings of the mask holes 32H. Eachfront surface opening H1 is an example of a first opening, and each backsurface opening H2 is an example of a second opening. In a plan view ofthe mask front surface 32F, the front surface opening H1 is larger insize than the back surface opening H2. Each mask hole 32H is a passagefor the vapor deposition particles sublimated from the vapor depositionsource. The vapor deposition particles sublimated from the vapordeposition source travel in the mask hole 32H from the front surfaceopening H1 toward the back surface opening H2. The mask hole 32H havingthe front surface opening H1 that is larger than the back surfaceopening H2 reduces the shadow effect for the vapor deposition particlesentering through the front surface opening H1.

In the mask front surface 32F, each front surface opening H1 is spacedapart from the other front surface openings H1. In other words, in themask front surface 32F, each front surface opening H1 is not connectedto the other front surface openings H1. Thus, in a plan view of the maskfront surface 32F, the sections of the mask portion 32 located betweenthe front surface openings H1 are unlikely to be thinner than thesection of the mask portion 32 that is free of mask holes 32H. Thisavoids reduction in mechanical strength of the mask portion 32. If onefront surface opening H1 is connected to another front surface openingH1 in the mask front surface 32F, the section where the two frontsurface openings H1 overlap would be thinner than the section of themask portion 32 that is free of mask holes 32H. This reduces themechanical strength of the mask portion 32 as compared to theconfiguration in which each front surface opening H1 is spaced apartfrom the other front surface openings H1.

When the mask portion 32 has a thickness of between 3 μm and 5 μminclusive, mask holes 32H that are usable to manufacture ahigh-resolution display device as described above can be formed simplyby wet-etching the mask sheet 32S from the mask front surface 32F.Further, when the mask portion 32 has a thickness of between 10 μm and15 μm inclusive, mask holes 32H that are usable to manufacture alow-resolution display device as described above can be formed simply bywet-etching the mask sheet 32S from the mask front surface 32F. That is,in either case, it is not necessary to wet-etch the mask sheet 32S fromthe mask back surface 32R.

In contrast, if a thicker mask sheet 32S is used to form a vapordeposition mask 30 for the manufacturing of a display device having acertain resolution, this mask sheet 32S needs to be wet-etched from boththe mask front surface 32F and the mask back surface 32R. When the masksheet 32S is wet-etched from both the mask front surface 32F and themask back surface 32R, each mask hole 32H has a shape in which a frontsurface recess, which includes a front surface opening H1, and a backsurface recess, which includes the back surface opening H2, areconnected to each other at the center of the mask portion 32 in thethickness direction. In each mask hole 32H, a section where the frontsurface recess is connected to the back surface recess is referred to asa connection section. The area of the mask hole 32H along the directionparallel to the mask front surface 32F is smallest in the connectionsection. The distance between the connection section and the backsurface opening H2 in the mask hole 32H is referred to as a step height.A greater step height increases the shadow effect described above. Incontrast, the mask portion 32 described above has zero step height. Assuch, the mask portion 32 advantageously limits the shadow effect.

[Mask Portion Joining Structure]

Referring to FIG. 3, the cross-sectional structure of the joiningbetween a mask portion 32 and a mask frame 31 is now described.

As shown in FIG. 3, each mask sheet 32S has an outer edge section 32E,which includes the edge of the mask sheet 32S. The outer edge section32E of the mask sheet 32S includes a region that is free of mask holes32H and extends continuously along the edge of the mask sheet 32S. Themask front surface 32F of the outer edge section 32E is joined to themask frame 31.

The mask frame 31 includes inner edge sections 31E, which define maskframe holes 33, a frame back surface 31R, which faces the mask sheet32S, and a frame front surface 31F, which is opposite to the frame backsurface 31R. Each inner edge section 31E includes a part of the frameback surface 31R and a part of the frame front surface 31F. Thethickness T31 of the mask frame 31, that is, the distance between theframe back surface 31R and the frame front surface 31F, is greater thanthe thickness T32 of the mask sheet 32S. This allows the mask frame 31to have a higher rigidity than the mask sheet 32S. In particular, themask frame 31 has a high rigidity that limits sagging of the inner edgesection 31E by its own weight and displacement of the inner edge section31E toward the mask portion 32.

The mask frame 31 is preferably made of an iron-nickel alloy, morepreferably an iron-nickel alloy that is used as the principal componentof the mask sheet 32S. That is, the mask frame 31 is preferably made ofInvar. The mask frame 31 is preferably at least twice as thick as themask portion 32.

The frame back surface 31R of each inner edge section 31E has a joiningsection 30BN where the mask front surface 32F is joined to the maskframe 31. The joining section 30BN extends continuously orintermittently along substantially the entire circumference of the inneredge section 31E. The joining section 30BN may be a welding mark formedby welding the frame back surface 31R to the mask front surface 32F.Alternatively, the joining section 30BN may be a joining layer that isformed separately from the mask frame 31 and the mask portion 32 to jointhe frame back surface 31R to the mask front surface 32F.

When each mask frame 31 is joined to the main frame 20, the main frame20 applies stress to the mask frame 31 that pulls the mask frame 31outward. In this step, the mask frame 31 may be joined to the main frame20 such that the ends of the mask frame 31 in the extending directionextend outward beyond the main frame 20.

The frame back surface 31R is a plane including the joining section 30BNand extends outward of the mask sheet 32S from the mask front surface32F of the outer edge section 32E. In other words, the inner edgesection 31E has a planar structure that virtually extends the mask frontsurface 32F outward, so that the inner edge section 31E extends from themask front surface 32F of the outer edge section 32E toward the outsideof the mask sheet 32S. Accordingly, in the area in which the frame backsurface 31R extends outward beyond the mask sheet 32S, a space V, whichcorresponds to the thickness of the mask sheet 32S, is likely to becreated around the mask sheet 32S. This limits physical interferencebetween the vapor deposition target S and the mask frame 31 around themask sheet 32S.

[Number of Mask Portions]

With reference to FIG. 4, the relationship between the number of maskholes 32H in a vapor deposition mask 30 and the number of mask holes 32Hin a mask portion 32 is now described.

As shown in FIG. 4A, each mask frame 31 may include three mask frameholes 33, which are an example of a plurality of mask frame holes 33. Asshown in FIG. 4B, each vapor deposition mask 30 includes one maskportion 32 for each mask frame hole 33. Specifically, the inner edgesection 31E defining a first mask frame hole 33A is joined to a firstmask portion 32A. The inner edge section 31E defining a second maskframe hole 33B is joined to a second mask portion 32B. The inner edgesection 31E defining a third mask frame hole 33C is joined to a thirdmask portion 32C.

The vapor deposition mask 30 is used repeatedly for a plurality of vapordeposition targets. Thus, the position and structure of the mask holes32H in the vapor deposition mask 30 need to be highly accurate. When thenumber of mask holes 32H required in one mask frame 31 is divided intothree mask portions 32 as described above, the following advantages areachieved. That is, in case one of the mask portions 32 is partiallydeformed, the size of a new mask portion 32 for replacing the deformedmask portion 32 may be reduced, as compared to a structure in which allthe mask holes 32H are formed in one mask portion 32. In addition, theconsumption of various materials associated with the manufacturing andrepair of the vapor deposition mask 30 may be lowered.

The structure of the mask holes 32H is inspected preferably while themask portions 32 are joined to the mask frame 31. For this reason, thejoining section 30BN preferably has a configuration that allows forreplacement of a deformed mask portion 32 with a new mask portion 32.Thus, one mask frame 31 can be used for a plurality of mask portions 32,and different mask portions 32 can be inspected using one mask frame 31.In addition, a thinner mask sheet 32S of the mask portion 32 and smallermask holes 32H tend to reduce the yield of the mask portion 32. Thus,the structure in which each of the mask frame holes 33 has one maskportion 32 is particularly suitable for a vapor deposition mask 30 thatrequires a high definition.

In the mask frame 31, the mask frame holes 33 form a mask hole row. Themask frame 31 is not limited to the configuration with one mask hole rowand may include a plurality of mask hole rows. That is, the vapordeposition mask 30 may include a plurality of rows of mask portions 32.

[Method for Manufacturing Vapor Deposition Mask]

Referring to FIGS. 5 and 6, a method for manufacturing the vapordeposition mask 30 is now described. FIG. 5 shows the step of preparinga substrate for producing mask portions 32 to the step of producing themask portions 32. FIG. 6 shows the step of joining the mask portions 32to the mask frame 31 to the step of removing the plastic layer from themask portions 32.

As shown in FIGS. 5A to 5F, the method for manufacturing the vapordeposition mask 30 first prepares a substrate 32K of a mask sheet 32S(see FIG. 5A). The substrate 32K of the mask sheet 32S includes a metalsheet 32S1, which is an example of a metal plate for forming a masksheet 32S, and also a plastic layer 41 and a glass substrate 42, whichsupport the metal sheet 32S1. Then, the thickness of the metal sheet32S1 is reduced (see FIG. 5B). The thickness of the metal sheet 32S1 ispreferably reduced to half or less the thickness of the metal sheet 32S1before etching. A resist layer PR is formed on the mask front surface32F of the metal sheet 32S1 (see FIG. 5C). The resist layer PR is thenexposed and developed, thereby forming a resist mask RM on the maskfront surface 32F (see FIG. 5D).

Then, the mask front surface 32F of the metal sheet 32S1 is wet-etchedusing the resist mask RM, forming a plurality of mask holes 32H in themetal sheet 32S1 (see FIG. 5E). In the wet etching of the metal sheet32S1, front surface openings H1 are first formed in the mask frontsurface 32F, and back surface openings H2, which are smaller in sizethan the front surface openings H1, are then formed in the mask backsurface 32R. Then, the resist mask RM is removed from the mask frontsurface 32F, completing a mask portion 32 formed of the mask sheet 32S(see FIG. 5F).

The step of preparing the substrate 32K includes a first joining step.The first joining step sandwiches the plastic layer 41 between the metalsheet 32S1 and the glass substrate 42 and joins the metal sheet 32S1 tothe glass substrate 42 with the plastic layer 41 in between. To join themetal sheet 32S1, the plastic layer 41, and the glass substrate 42together, a chemical bonding (CB) process is first applied to thesurfaces of the metal sheet 32S1 and the glass substrate 42 that arebrought into contact at least with the plastic layer 41. The surfaces ofthe metal sheet 32S1 and the glass substrate 42 that are subjected tothe CB process are target surfaces. In the CB process, a chemicalsolution may be applied to the target surfaces to provide the targetsurfaces with a functional group reactive with the plastic layer 41. Forexample, the CB process applies a hydroxyl group to the target surfaces.The metal sheet 32S1, the plastic layer 41, and the glass substrate 42are layered in this order and subjected to thermocompression bonding.The functional group on the target surfaces reacts with the functionalgroup on the surfaces of the plastic layer 41, thereby bonding theplastic layer 41 to the metal sheet 32S1 and to the glass substrate 42.In the first joining step, the metal sheet 32S1 that is joined to theglass substrate 42 with the plastic layer 41 in between preferably has athickness of greater than or equal to 10 μm.

The plastic layer 41 is preferably made of polyimide. This allows themetal sheet 32S1, the plastic layer 41, and the glass substrate 42 tohave similar thermal expansion coefficients. Consequently, in theprocess of manufacturing the vapor deposition mask 30, the laminate ofthe metal sheet 32S1, the plastic layer 41, and the glass substrate 42is unlikely to warp when heated, which would be otherwise caused by adifference in thermal expansion coefficient between the layers of thelaminate.

Electrolysis or rolling is used to produce the metal sheet 32S1. Themetal sheet 32S1 obtained by electrolysis or rolling may be subjected topost-treatment, such as polishing or annealing.

When electrolysis is used to produce the metal sheet 32S1, the metalsheet 32S1 is formed on the surface of the electrode used forelectrolysis. The metal sheet 32S1 is then removed from the surface ofthe electrode. The metal sheet 32S1 is thus produced.

When rolling is used to produce the metal sheet 32S1, the metal sheet32S1 preferably has a thickness of greater than or equal to 15 μm. Whenelectrolysis is used to produce the metal sheet 32S1, the metal sheet32S1 preferably has a thickness of greater than or equal to 10 μm

The electrolytic bath for electrolysis contains an iron ion source, anickel ion source, and a pH buffer. The electrolytic bath may alsocontain a stress relief agent, an Fe³⁺ ion masking agent, and acomplexing agent, for example. The electrolytic bath is a weakly acidicsolution having a pH adjusted for electrolysis. Examples of the iron ionsource include ferrous sulfate heptahydrate, ferrous chloride, andferrous sulfamate. Examples of the nickel ion source include nickel (II)sulfate, nickel (II) chloride, nickel sulfamate, and nickel bromide.Examples of the pH buffer include boric acid and malonic acid. Malonicacid also functions as an Fe³⁺ ion masking agent. The stress reliefagent may be saccharin sodium, for example. The complexing agent may bemalic acid or citric acid. The electrolytic bath used for electrolysismay be an aqueous solution containing additives listed above. Theelectrolytic bath is adjusted using a pH adjusting agent to have a pH ofbetween 2 and 3 inclusive, for example. The pH adjusting agent may be 5%sulfuric acid or nickel carbonate.

The conditions for electrolysis are set to achieve desired values ofthickness and composition ratio of the metal sheet 32S1. Theseconditions include the temperature of the electrolytic bath, the currentdensity, and the electrolysis time. The temperature of the electrolyticbath may be between 40° C. and 60° C. inclusive. The current density maybe between 1 A/dm² and 4 A/dm² inclusive. The anode used in theelectrolytic bath may be a pure iron plate or a nickel plate, forexample. The cathode used in the electrolytic bath may be a plate ofstainless steel such as SUS304.

When rolling is used to produce the metal sheet 32S1, a base materialfor manufacturing the metal sheet 32S1 is first rolled. The rolled basematerial is annealed to obtain the metal sheet 32S1. When the basematerial, which is to be rolled to form the metal sheet 32S1, is formed,a deoxidizer is mixed into the constituents of the base material forrolling so as to remove the oxygen trapped in the constituents. Thedeoxidizer may be granular aluminum or magnesium. The aluminum ormagnesium reacts with the oxygen in the base material and is containedin the base material as a metallic oxide such as an aluminum oxide or amagnesium oxide. While most of the metallic oxide is removed from thebase material before rolling, some of the metallic oxide remains in thebase material to be rolled. In this respect, a method for manufacturingthe mask portion 32 using electrolysis limits mixing of the metallicoxide into the mask sheet 32S.

The thinning step etches the metal sheet 32S1 to reduce the thickness ofthe metal sheet 32S1 before the metal sheet 32S1 forms the mask portion32. The thinning step may use wet etching. The thinning step preferablyreduces the thickness of the metal sheet 32S1 to half or less thethickness of the metal sheet 32S1 before thinning. This allows the metalsheet 32S1 used in the first joining step to be at least twice as thickas the mask portion 32. Thus, even when the mask portion 32 is requiredto have a thickness of less than or equal to 15 μm as described above,the metal sheet 32S1 that has a higher rigidity than the mask portion 32of the vapor deposition mask 30 is used before the metal sheet 32S1 isjoined to the glass substrate 42 in the first joining step. Thisfacilitates the joining of the metal sheet 32S1 to the glass substrate42 as compared to a configuration in which the metal sheet 32S1 that isjoined to the glass substrate 42 has the same thickness as the maskportion 32. The step of reducing the thickness of the metal sheet 32S1may be omitted.

In the thinning step, any acidic etchant may be used as the etchant forwet-etching the metal sheet 32S1. When the metal sheet 32S1 is made ofInvar, any etchant can be used that is capable of etching Invar. Theacidic etchant may be a solution containing perchloric acid,hydrochloric acid, sulfuric acid, formic acid, or acetic acid mixed in aferric perchlorate solution or a mixture of a ferric perchloratesolution and a ferric chloride solution. The metal sheet 32S1 may beetched by a dipping method, a spraying method, or a spinning method.

An acidic etchant may be used to form a plurality of mask holes 32H inthe metal sheet 32S1 by etching. When the metal sheet 32S1 is made ofInvar, any of the etchants that are usable in the thinning stepdescribed above can be used. In addition, any of the methods usable inthe thinning step may be used to etch the mask front surface 32F.

As described above, when the thickness of the metal sheet 32S1 isbetween 3 μm and 5 μm inclusive, a plurality of mask holes 32H may beformed such that 700 or more and 1000 or less mask holes 32H arearranged per inch in a plan view of the mask front surface 32F of themetal sheet 32S1. That is, a mask portion 32 is obtained that can beused to form a display device having a resolution of between 700 ppi and1000 ppi inclusive. In other words, a plurality of mask holes 32H can beformed such that 700 or more and 1000 or less mask holes 32H arearranged per inch in the direction along the mask front surface 32F ofthe mask portion 32.

Further, when the thickness of the metal sheet 32S1 is between 10 μm and15 μm inclusive, a plurality of mask holes 32H may be formed such that300 or more and 400 or less mask holes 32H are arranged per inch in aplan view of the mask front surface 32F of the metal sheet 32S1. Thatis, a mask portion 32 is obtained that can be used to form a displaydevice having a resolution of 300 ppi to 400 ppi inclusive. In otherwords, a plurality of mask holes 32H can be formed such that 300 or moreand 400 or less mask holes 32H are arranged per inch in the directionalong the mask front surface 32F of the mask portion 32.

The step of preparing the substrate 32K may include a step of thinningthe metal sheet 32S1 from one surface of the metal sheet 32S1 before thefirst joining step. In this case, the thinning step included in the stepof preparing the substrate 32K is a first thinning step, and thethinning step performed after the step of preparing the substrate 32K isa second thinning step.

The metal sheet 32S1 includes a first surface and a second surface,which is opposite to the first surface. In the first thinning step, themetal sheet 32S1 is thinned by etching on the first surface. In thesecond thinning step, the metal sheet 32S1 is thinned by etching on thesecond surface. The surface formed by etching on the first surface isthe surface of the metal sheet 32S1 that is joined to the plastic layer41 and also subjected to the CB process.

Etching both the first and second surfaces of the metal sheet 32S1allows the residual stress of the metal sheet 32S1 to be adjusted fromboth the first and second surfaces. This limits imbalance in theresidual stress of the metal sheet 32S1 after etching, as compared to aconfiguration that etches only the second surface. Consequently, whenthe mask portion 32 obtained from the metal sheet 32S1 is joined to themask frame 31, the mask portion 32 is less likely to have creases. Thesurface of the metal sheet 32S1 that is obtained by etching the firstsurface corresponds to the mask back surface 32R of the mask sheet 32S,and the surface obtained by etching the second surface corresponds tothe mask front surface 32F of the mask sheet 32S.

The amount of etching on the first surface of the metal sheet 32S1 is afirst etching amount, and the amount of etching on the second surface ofthe metal sheet 32S1 is a second etching amount. The first etchingamount and the second etching amount may be the same or different. Whenthe first etching amount differs from the second etching amount, thefirst etching amount may be larger than the second etching amount, orthe second etching amount may be larger than the first etching amount.When the second etching amount is larger than the first etching amount,the amount of etching performed while the metal sheet 32S1 is supportedby the plastic layer 41 and the glass substrate 42 is larger, increasingthe handleability of the metal sheet 32S1. This facilitates the etchingof the metal sheet 32S1.

In order to reduce the residual stress of the metal sheet 32S1 and toreduce the metallic oxide contained in the metal sheet 32S1 obtained byrolling, the first etching amount and the second etching amount arepreferably greater than or equal to 3 μm.

As shown in FIGS. 6A to 6C, the mask front surfaces 32F of the outeredge sections 32E are joined to the inner edge sections 31E (see FIG.6A). Then, the glass substrates 42 joined to the respective plasticlayers 41 are peeled off from the plastic layers 41 (see FIG. 6B). Theplastic layers 41 joined to the respective mask portions 32 are thenpeeled off from the mask portions 32 (see FIG. 6C). The vapor depositionmask 30 is thus obtained.

The step of joining a part of each mask portion 32 to a part of the maskframe 31 includes a second joining step. The second joining step joinsthe mask frame 31 to the surface of the mask portion 32 opposite to thesurface that is in contact with the plastic layer 41. As describedabove, the mask frame 31 is preferably made of an iron-nickel alloy, andthe mask frame 31 is preferably at least twice as thick as the maskportion 32. This enhances the mechanical strength of the vapordeposition mask 30. Further, when vapor deposition is performed usingthe vapor deposition mask 30, the mask portion 32 is unlikely to warp,which would be otherwise caused by a difference in thermal expansioncoefficient between the mask frame 31 and the mask portion 32. Thisavoids reduction in the accuracy of the shape of pattern formed usingthe vapor deposition mask 30.

As described above, when the thickness of the mask portion 32 is between3 μm and 15 μm inclusive, the thickness of the mask frame 31 ispreferably between 15 μm and 200 μm inclusive, and the mask frame 31 ispreferably at least twice as thick as the mask portion 32. For the vapordeposition mask 30 including the mask portions 32 usable to manufacturehigh-resolution display devices, the thickness of each mask frame 31 ispreferably at least ten times thicker than the mask portion 32. Forexample, the thickness of the mask portion 32 is preferably between 3 μmand 5 μm inclusive, and the thickness of the mask frame 31 is preferablybetween 50 μm and 200 μm inclusive. Although the mask portion 32 isextremely thin, the mask frame 31 that is at least ten times thickerthan the mask portion 32 avoids reduction in the overall mechanicalstrength of the vapor deposition mask 30.

As described above, laser welding can be used to join the outer edgesection 32E to the inner edge section 31E. The section of the maskportion 32 corresponding to the joining section 30BN is irradiated witha laser beam L through the glass substrate 42 and the plastic layer 41.As such, the glass substrate 42 and the plastic layer 41 allow the laserbeam L to pass through. In other words, the laser beam L has awavelength that can pass through the glass substrate 42 and the plasticlayer 41. Intermittent joining sections 30BN are formed by applying thelaser beam L intermittently along the edge defining the mask frame hole33. A continuous joining section 30BN is formed by applying the laserbeam L continuously along the edge defining the mask frame hole 33. Theouter edge section 32E is thus welded to the inner edge section 31E.When the plastic layer 41 and the glass substrate 42 support the maskportion 32 with stress acting on the mask portion 32 outward of the maskportion 32, the welding between the mask portion 32 and the mask frame31 does not have to involve application of stress to the mask portion32.

The method for manufacturing the vapor deposition mask 30 includes apeeling step. The peeling step peels off the plastic layer 41 and theglass substrate 42 from the mask portion 32. In the process ofmanufacturing the vapor deposition mask 30, the plastic layer 41 and theglass substrate 42 support the mask portion 32 including the mask holes32H. In the vapor deposition mask 30, the mask frame 31 supports themask portion 32. This allows the mask portion 32 to be thinner than thatin a configuration in which the vapor deposition mask 30 consists onlyof the mask portion 32. Accordingly, the shortened distance from oneopening to the other of each mask hole 32H improves the accuracy of thestructure of the pattern formed using the vapor deposition mask 30,while the rigidity of the mask frame 31 improves the handleability ofthe vapor deposition mask 30.

The peeling step includes a first peeling step and a second peelingstep. The first peeling step peels off the glass substrate 42 from theplastic layer 41 by irradiating the interface between the plastic layer41 and the glass substrate 42 with the laser beam L having a wavelengththat passes through the glass substrate 42 and is absorbed by theplastic layer 41.

The first peeling step applies the laser beam L to the interface betweenthe plastic layer 41 and the glass substrate 42 so that the plasticlayer 41 absorbs the heat energy of the laser beam L. This heats theplastic layer 41 and weakens the strength of the chemical bondingbetween the plastic layer 41 and the glass substrate 42. The glasssubstrate 42 is then peeled off from the plastic layer 41. In the firstpeeling step, the entire joining section 30BN is preferably irradiatedwith the laser beam L. However, only a part of the joining section 30BNmay be irradiated with the laser beam L if the strength of bondingbetween the glass substrate 42 and the plastic layer 41 is weakened inthe entire joining section 30BN.

The glass substrate 42 preferably has a higher transmittance than theplastic layer 41 at the wavelength of the laser beam L. This increasesthe efficiency in heating the section of the plastic layer 41 that formsthe interface between the glass substrate 42 and the plastic layer 41,as compared to a configuration in which the plastic layer 41 has ahigher transmittance than the glass substrate 42.

When the wavelength of the laser beam L is between 308 nm and 355 nminclusive, for example, the glass substrate 42 preferably has atransmittance of greater than or equal to 54%, and the plastic layer 41preferably has a transmittance of less than or equal to 1% at thiswavelength. As a result, more than half the light quantity of laser beamL applied to the glass substrate 42 passes through the glass substrate42, and the plastic layer 41 absorbs most of the laser beam L that haspassed through the glass substrate 42. This further increases theefficiency in heating the section of the plastic layer 41 forming theinterface between the glass substrate 42 and the plastic layer 41.

As described above, the plastic layer 41 is preferably made ofpolyimide. In particular, the plastic layer 41 is preferably made of acolored polyimide. The glass substrate 42 is preferably transparent.Examples of the material used for the glass substrate 42 include quartzglass, non-alkali glass, and soda-lime glass.

After the first peeling step, the second peeling step peels off theplastic layer 41 from the mask portion 32 by dissolving the plasticlayer 41 using a chemical solution LM. As the chemical solution LM, aliquid may be used that can dissolve the material of the plastic layer41 and that is not reactive with the material of the mask portion 32.The chemical solution LM may be an alkaline solution, for example. Thealkaline solution may be an aqueous sodium hydroxide solution. Theexample shown in FIG. 6C uses a dipping method to bring the plasticlayer 41 into contact with the chemical solution LM. However, a sprayingmethod and a spinning method may be used to bring the plastic layer 41into contact with the chemical solution LM.

In the process of peeling off the plastic layer 41 and the glasssubstrate 42 from the mask portion 32, the first peeling step peels offthe glass substrate 42 from the plastic layer 41, and the second peelingstep peels off the plastic layer 41 from the mask portion 32. Thisreduces the external force acting on the mask portion 32, as compared toa configuration that applies external force to the laminate of the glasssubstrate 42, the plastic layer 41, and the mask portion 32 to causeinterface failure to peel off the glass substrate 42 and the plasticlayer 41 from the mask portion 32. As a result, the peeling of theplastic layer 41 and the glass substrate 42 is less likely to deform themask portion 32, and ultimately less likely to deform the mask holes 32Hin the mask portion 32.

In the method of manufacturing a display device using the vapordeposition mask 30 described above, the mask device 10 in which thevapor deposition mask 30 is set is placed in a vacuum chamber of thevapor deposition apparatus. At this time, the mask device 10 is set inthe vacuum chamber such that the mask back surface 32R faces the vapordeposition target, such as a glass substrate, and that the mask frontsurface 32F faces the vapor deposition source. Then, the vapordeposition target S is placed in the vacuum chamber, and the vapordeposition material is sublimated from the vapor deposition source. Thisforms a pattern of the shape corresponding to the back surface openingH2 on the vapor deposition target facing the back surface opening H2.The vapor deposition material may be an organic light-emitting materialfor forming pixels of a display device, or a material of a pixelelectrode for forming a pixel circuit of a display device, for example.

[Test Examples]

Referring to FIGS. 7 to 9, test examples are now described. In FIGS. 8and 9, each region surrounded by the long dashed double-short dashedline is a wavelength band of between 308 nm and 355 nm inclusive.

[Relationship between Laser Beam Wavelength and Pattern Position]

First, test plates, which were thin metal plates, were prepared. Eachtest plate had a central section and an outer section surrounding thecentral section. In the test plate, the central section had a pluralityof patterns for measurement of the positional accuracy, and the outersection was free of a pattern. As the lasers to apply laser beams totest plates, a laser emitting a laser beam having a wavelength of 1064nm and a laser emitting a laser beam having a wavelength of 355 nm wereprepared.

Each laser emitted a laser beam to the outer section of each test platealong one straight line. By applying a laser beam, a plurality ofirradiated sections each having a length of 0.1 mm were formed atintervals of 0.5 mm. For each test plate, the state before laser beamirradiation and the state after laser beam irradiation were photographedusing a CNC image measuring system (VMR-6555, manufactured by NikonCorporation). The amount of displacement of the pattern closest to theouter section between the test plate before irradiation and the testplate after irradiation was determined.

As shown in FIG. 7, when a test plate was irradiated with a laser beamof 1062 nm, the amount of displacement was 2.7 μm. When a test plate wasirradiated with a laser beam of 355 nm, the amount of displacement was0.27 μm.

The first peeling step directs a laser beam toward the mask portionthrough the glass substrate and the plastic layer. As such, the glasssubstrate and the plastic layer absorb most of the laser beam directedtoward the mask portion. Nevertheless, the laser beam directed towardthe mask portion should not displace the pattern of the mask portion incase the mask portion is irradiated with the laser beam. For thisreason, the laser beam used in the first peeling step preferably has awavelength of less than or equal to 355 nm.

[Transmittance of Glass Substrate and Plastic Layer]

Glass substrates A, B and C were prepared, and their transmittance ateach wavelength was measured. Glass substrate A was a quartz glasssubstrate having a thickness of 2.3 mm (SMS6009E5, manufactured byShin-Etsu Chemical Co., Ltd.). Glass substrate B was a non-alkali glasssubstrate having a thickness of 0.7 mm (OA-10G, manufactured by NipponElectric Glass Co., Ltd.). Glass substrate C was a substrate made ofsoda-lime glass having a thickness of 2.3 mm (soda-lime glass,manufactured by Central Glass Co., Ltd.).

The transmittance of each glass substrate was measured using aspectrophotometer (U-4100, manufactured by Hitachi, Ltd.). Thetransmittances of the glass substrates were measured using a wavelengthrange of between 200 nm and 800 nm inclusive and using thetransmittances in the atmosphere as reference values. FIG. 8 shows themeasurement results of the transmittances of the glass substrates.

As shown in FIG. 8, the transmittance of Glass substrate A was observedto be substantially constant regardless of the wavelength of light. Thetransmittance of Glass substrate B was observed to rise sharply in awavelength band of between 250 nm and 350 nm inclusive. Thetransmittance of Glass substrate C was observed to rise sharply in awavelength band of between 300 nm and 350 nm inclusive.

Plastic layers A, B and C were prepared, and their transmittance at eachwavelength was measured. Plastic layer A was a colored polyimide plasticlayer (Kapton (registered trademark) EN, manufactured by DU PONT-TORAYCO., LTD.). Plastic layer B was a colored polyimide plastic layer(Upilex (registered trademark) VT, manufactured by Ube Industries,Ltd.). Plastic layer C was a transparent polyimide plastic layer(Neoprim (registered trademark), manufactured by MITSUBISHI GAS CHEMICALCOMPANY, INC.). All the plastic layers had a thickness of 25 μm.

The transmittance of each plastic layer was measured using aspectrophotometer (same as above). In the same manner as the glasssubstrates, the transmittances of the plastic layers were measured usinga wavelength range of between 200 nm and 800 nm inclusive and using thetransmittances in the atmosphere as reference values. FIG. 9 shows themeasurement results of the transmittances of the plastic layers.

As shown in FIG. 9, the transmittances of Plastic layers A and B wereobserved to rise sharply in a wavelength band of between 400 nm and 500nm inclusive. In contrast, the transmittance of Plastic layer C wasobserved to rise sharply in a wavelength band of between 300 nm and 350nm inclusive.

In the first peeling step described above, a laser beam having awavelength between 308 nm and 355 nm inclusive can be used. According tothe measurement results, at 308 nm, the transmittance of Plastic layer Awas 0.1%, the transmittance of Plastic layer B was 0.0%, and thetransmittance of Plastic layer C was 0.1%. At 308 nm, the transmittanceof Glass substrate A was 92.7%, the transmittance of Glass substrate Bwas 54.7%, and the transmittance of Glass substrate C was 1.3%. At 355nm, the transmittance of Plastic layer A was 0.0%, the transmittance ofPlastic layer B was 0.0%, and the transmittance of Plastic layer C was85.1%. At 355 nm, the transmittance of Glass substrate A was 93.3%, thetransmittance of Glass substrate B was 86.5%, and the transmittance ofGlass substrate C was 83.4%.

In the first peeling step, in order to increase the efficiency of theplastic layer in absorbing the laser beam, the transmittance of theglass substrate is preferably higher than and significantly differentfrom the transmittance of the plastic layer at the wavelength of thelaser beam used in the first peeling step. In this regard, when thewavelength of the laser beam is 355 nm, one of Plastic layers A and B ispreferably used as the plastic layer, and one of Glass substrates A to Cis preferably used as the glass substrate. When the wavelength of thelaser beam is 308 nm, one of Plastic layers A to C is preferably used asthe plastic layer, and one of Glass substrates A and B is preferablyused as the glass substrate.

As described above, the present embodiment of a method for manufacturinga vapor deposition mask has the following advantages.

(1) In the process of manufacturing the vapor deposition mask 30, theplastic layer 41 and the glass substrate 42 support the mask portion 32having a plurality of mask holes 32H. In the vapor deposition mask 30,the mask frame 31 supports the mask portions 32. This allows the maskportion 32 to be thinner than that in a configuration in which the vapordeposition mask 30 consists only of the mask portion 32. Consequently,the shortened distance from one opening to the other of each mask hole32H improves the accuracy of the structure of the pattern formed usingthe vapor deposition mask 30, while the rigidity of the mask frame 31improves the handleability of the vapor deposition mask 30.

(2) The external force acting on the mask portion 32 is reduced ascompared to a configuration that applies external force to the laminateof the glass substrate 42, the plastic layer 41, and the mask portion 32to cause interface failure to peel off the glass substrate 42 and theplastic layer 41 from the mask portion 32. As a result, the peeling ofthe plastic layer 41 and the glass substrate 42 is less likely to deformthe mask portion 32, and ultimately less likely to deform the mask holes32H in the mask portion 32.

(3) The plastic layer 41 has a lower transmittance than the glasssubstrate 42. This increases the efficiency in heating the section ofthe plastic layer 41 that forms the interface between the glasssubstrate 42 and the plastic layer 41, as compared to a configuration inwhich the plastic layer 41 has a higher transmittance than the glasssubstrate 42.

(4) More than half the light quantity of laser beam L directed towardthe glass substrate 42 passes through the glass substrate 42, and theplastic layer 41 absorbs most of the laser beam L that has passedthrough the glass substrate 42. This increases the efficiency in heatingthe section of the plastic layer 41 that forms the interface between theglass substrate 42 and the plastic layer 41.

(5) The mask portions 32 and the mask frame 31 are both made of aniron-nickel alloy, and the mask frame 31 is at least twice as thick asthe mask portions 32. This enhances the mechanical strength of the vapordeposition mask 30.

(6) When the vapor deposition mask 30 is used for vapor deposition, themask portions 32 are unlikely to warp, which would be otherwise causedby a difference in thermal expansion coefficient between the mask frame31 and the mask portions 32. This avoids reduction in the accuracy ofthe shape of pattern formed using the vapor deposition mask 30.

(7) Even when the thickness of the mask portion 32 is extremely thin,the mask frame 31 that is at least ten times thicker than the maskportion 32 avoids reduction in the overall mechanical strength of thevapor deposition mask 30.

(8) The metal sheet 32S1 has a higher rigidity than the mask portion 32of the vapor deposition mask 30. This facilitates the joining of themetal sheet 32S1 to the glass substrate 42 as compared to aconfiguration in which the metal sheet 32S1 joined to the glasssubstrate 42 has the same thickness as the mask portion 32.

(9) In the process of manufacturing the vapor deposition mask 30,heating the laminate of the mask sheet 32S, the plastic layer 41, andthe glass substrate 42 is unlikely to warp the laminate, which would beotherwise caused by a difference in thermal expansion coefficientbetween the layers of the laminate.

(10) Etching the metal sheet 32S1 from the first and second surfacesreduces the thickness of the metal sheet 32S1 and also the residualstress of the metal sheet 32S1.

The above-described embodiment may be modified as follows.

The plastic layer 41 may be made from a plastic other than polyimide aslong as it is removable from the mask portion 32. Nevertheless, to limitheat-induced warpage of the laminate of the mask portion 32, the plasticlayer 41, and the glass substrate 42, the plastic layer 41 is preferablymade of polyimide as described above.

The metal sheet 32S1, which is joined to the glass substrate 42 with theplastic layer 41 in between in the first joining step, may have athickness of less than or equal to 30 μm.

Provided that the mask frame 31 has a higher rigidity than the maskportion 32, the mask frame 31 may have a thickness of less than or equalto 50 μm. Further, the mask frame 31 may be made of a metal other thanInvar.

The first peeling step may use a laser beam L that has a wavelength ofless than 308 nm or greater than 355 nm, as long as the irradiation withthe laser beam L can reduce the strength of bonding between the plasticlayer 41 and the glass substrate 42. Further, the transmittances of theplastic layer 41 and the glass substrate 42 for the laser beam L may beany values that allow the laser beam L to be absorbed by the plasticlayer 41 so as to weaken the adhesion between the plastic layer 41 andthe glass substrate 42. That is, the transmittance of the plastic layer41 and the transmittance of the glass substrate 42 for the laser beam Lare not limited to the values described above.

The first peeling step may be a step of peeling off the glass substrate42 from the plastic layer 41 by a method other than the irradiation withthe laser beam L. For example, the first peeling step may use a chemicalsolution to peel off the glass substrate 42 from the plastic layer 41.Alternatively, the first peeling step may physically peel off the glasssubstrate 42 from the plastic layer 41 by applying an external forcebetween the glass substrate 42 and the plastic layer 41.

The plastic layer 41 and the glass substrate 42 may be peeled off fromthe mask sheet 32S at the same time. In other words, the plastic layer41 and the glass substrate 42 may be peeled off from the mask sheet 32Sin a single step. For example, the plastic layer 41 and the glasssubstrate 42 may be peeled off from the mask sheet 32S in a single stepby using a chemical solution that dissolves the plastic layer 41.

The mask holes 32H in the metal sheet 32S1 do not have to be formed bywet etching using an etchant, and may be formed by applying laser beamsto the metal sheet 32S1.

DESCRIPTION OF THE REFERENCE NUMERALS

10 . . . Mask Device; 20 . . . Main Frame; 21 . . . Main Frame Hole; 30. . . Vapor Deposition Mask; 30BN . . . Joining Section; 31 . . . MaskFrame; 31E . . . Inner Edge Section; 31F . . . Frame Front Surface; 31R. . . Frame Back Surface; 32 . . . Mask Portion; 32E . . . Outer EdgeSection; 32F . . . Mask Front Surface; 32H . . . Mask Hole; 32K . . .Substrate; 32R . . . Mask Back Surface; 32S . . . Mask Sheet; 32S1 . . .Metal Sheet; 33 . . . Mask Frame Hole; 41 . . . Plastic Layer; 42 . . .Glass Substrate; H1 . . . Front Surface Opening; H2 . . . Back SurfaceOpening; PR . . . Resist Layer; RM . . . Resist Mask; S . . . VaporDeposition Target; V . . . Space

1. A method for manufacturing a vapor deposition mask including a maskportion that is formed from a metal plate made of an iron-nickel alloyand has a plurality of mask holes, the method comprising: sandwiching aplastic layer between a glass substrate and a metal plate made of aniron-nickel alloy and joining the metal plate to the glass substratewith the plastic layer in between; forming a mask portion including aplurality of mask holes from the metal plate; joining a surface of themask portion that is opposite to a surface of the mask portion that isin contact with the plastic layer to a mask frame, which has a higherrigidity than the mask portion and is in a shape of a frame surroundingthe mask holes of the mask portion; and peeling off the plastic layerand the glass substrate from the mask portion.
 2. The method formanufacturing a vapor deposition mask according to claim 1, whereinpeeling off the plastic layer and the glass substrate includes peelingoff the glass substrate from the plastic layer by irradiating aninterface between the plastic layer and the glass substrate with a laserbeam having a wavelength that passes through the glass substrate and isabsorbed by the plastic layer, and peeling off the plastic layer fromthe mask portion by dissolving the plastic layer using a chemicalsolution after peeling off the glass substrate from the plastic layer.3. The method for manufacturing a vapor deposition mask according toclaim 2, wherein at the wavelength of the laser beam, the glasssubstrate has a higher transmittance than the plastic layer.
 4. Themethod for manufacturing a vapor deposition mask according to claim 3,wherein the wavelength of the laser beam is between 308 nm and 355 nminclusive, the transmittance of the glass substrate at the wavelength isgreater than or equal to 54%, and the transmittance of the plastic layerat the wavelength is less than or equal to 1%.
 5. The method formanufacturing a vapor deposition mask according to claim 1, wherein themask frame is made of an iron-nickel alloy, and a ratio of a thicknessof the mask frame to a thickness of the mask portion is greater than orequal to
 2. 6. The method for manufacturing a vapor deposition maskaccording to claim 5, wherein the thickness of the mask frame is between50 μm and 200 μm inclusive, the thickness of the mask portion is between3 μm and 5 μm inclusive, and forming the mask portion includes formingthe mask holes such that 700 or more and 1000 or less mask holes arearranged per inch in a direction along a surface of the mask portion. 7.The method for manufacturing a vapor deposition mask according to claim1, wherein joining the metal plate to the glass substrate with theplastic layer in between includes joining the metal plate having athickness of greater than or equal to 10 μm to the glass substrate withthe plastic layer in between, and the method further comprises etchingthe metal plate before the mask portion is formed from the metal plateto reduce a thickness of the metal plate to half or less of a thicknessof the metal plate before etching.
 8. The method for manufacturing avapor deposition mask according to claim 1, wherein the plastic layer ismade of polyimide.
 9. The method for manufacturing a vapor depositionmask according to claim 1, wherein the metal plate includes a firstsurface and a second surface, the method further comprises etching themetal plate from the first surface before joining the metal plate to theglass substrate, joining the metal plate to the glass substrate includesjoining a surface obtained after the first surface is etched to theglass substrate with the plastic layer in between, and the methodfurther comprises etching the metal plate from the second surface afterthe metal plate is joined to the glass substrate.